Blood Smear
A blood smear is a technique used for blood analysis in which a thin layer of cells is examined. This study provides information about red blood cells, white blood cells, and platelets.
General Description
A blood smear is a procedure performed in clinical laboratories to study the quantity and shape of blood cells. This type of test, also known as a peripheral blood smear, is typically conducted when a complete blood count (CBC) has shown abnormal results, as part of routine analysis, or to diagnose hematological disorders.
In a blood smear, red blood cells, white blood cells, and platelets—the three main types of blood cells—are analyzed.
Abnormal blood smear results may indicate various conditions:
- Red blood cell abnormalities: Liver disease, hemolytic anemia, iron deficiency anemia, liver disease, thalassemia, or bone metastases.
- White blood cell abnormalities: Infections, inflammatory processes, or leukemia.
- Platelet changes: Platelet disorders or thrombocytopenia.
When Is It Indicated?
A blood smear is used to diagnose or monitor various blood conditions, kidney failure, malaria, or certain types of cancer. It may also be used to assess the damage caused by the side effects of chemotherapy.
Some symptoms that may prompt a doctor to order a blood smear include anemia, frequent bruising, fatigue, jaundice, unusual bleeding, or recurrent unexplained fever.
How Is It Performed?
First, a peripheral blood sample is taken following the same procedure as for routine blood tests.
In the laboratory, the following procedure is carried out:
- A drop of blood is placed at the edge of a glass slide and spread across the surface using another slide. Then, a stain is applied to facilitate cell observation.
- The appropriate area for examination is identified—one where the cells are undamaged and sufficiently separated to distinguish them clearly.
- The sample is observed under a microscope to determine whether the shape and size of blood components are altered and whether the count is within normal values.
Risks
There are no risks associated with a blood smear.
Side effects are related to the blood draw procedure itself, as bruising may occur at the puncture site or dizziness may develop. In both cases, these are mild discomforts that resolve quickly.
What To Expect From A Blood Smear
During a blood smear test, the patient is only present for the sample collection. The blood draw follows this process:
- The patient sits or reclines slightly on an examination table. Those prone to dizziness should inform the medical staff beforehand so they can remain lying down during and after the procedure.
- The arm is exposed and extended.
- The specialist disinfects the area and places a tourniquet above the elbow to facilitate blood flow.
- A needle is inserted into a vein, usually in the inner elbow, the tourniquet is removed, and the syringe plunger is pulled to draw a small amount of blood.
- A sterile gauze pad is applied to the puncture site, and pressure is maintained for a few minutes to minimize the risk of bruising.
The patient can resume normal activities after the procedure, which typically takes about five minutes. It is recommended to drink plenty of fluids in the following hours to help the body replenish the extracted blood more quickly.
The test results are usually available in approximately one week.
Specialties That Request A Blood Smear
A blood smear is performed by hematology specialists and may be requested by oncologists, general practitioners, hepatologists, and other specialists.
How to prepare
In general, no special preparation is required for a blood smear. However, in some cases, it may be necessary to suspend certain medications to avoid altered results. If this is required, the specialist will inform the patient in advance.
